Mathematical genetic models of X-chromosome transmission and studies of genetic linkage to X-chromosome markers are being performed in primary affective disorders. Two new mathematical models for analysis of two generation data and linkage studies have been developed. The first takes penetrance and variable age of onset into account and also gives more precise opportunities for ascertainment analysis. The second takes into account familial non-X-chromosome illness as a source of heterogeneity in the data, and represents a new theoretical development. Family study data and data on Xg blood group antigen and color blindness markers of the X-chromosome are currently being collected. Neither Xg nor color blindness is linked to bipolar affective disorder in our preliminary data analysis. BIBLIOGRAPHIC REFERENCES: Gershon, E.S., Belmaker, R.H., Kety, S.S. and Rosenbaum, M. (Editors): Impact of biology on modern psychiatry. Plenum Press, N.Y. 1977. Gershon, E.S.: Genetic and Biologic Studies of Affective Illness. In Impact of biology on modern psychiatry, Gershon, E.S., Belmaker, R.H., Kety, S.S. and Rosenbaum, M. (Eds.) Plenum Press, N. Y. pp. 207-228, 1977.